Phenotypic plasticity can enhance a species’ ability to persist in a new and stressful environment, so that reaction norms are expected to evolve as organisms encounter novel environments. Biological invasions provide a robust system to investigate such changes. We measured the rates of early growth and development in tadpoles of invasive cane toads (Rhinella marina) in Australia, from a range of locations and at different larval densities. Populations in long-colonized areas have had the opportunity to adapt to local conditions, whereas at the expanding range edge, the invader is likely to encounter challenges that are both novel and unpredictable. We thus expected invasion-vanguard populations to exhibit less phenotypic plasticity than range-core populations. Compared to clutches from long-colonized areas, clutches from the invasion front were indeed less plastic (i.e. rates of larval growth and development were less sensitive to density). In contrast, those rates were highly variable in clutches from the invasion front, even among siblings from the same clutch under standard conditions. Clutches with highly variable rates of growth and development under constant conditions had lower phenotypic plasticity, suggesting a trade-off between these two strategies. Although these results reveal a strong pattern, further investigation is needed to determine whether these different developmental strategies are adaptive (i.e. adaptive phenotypic plasticity vs. bet-hedging) or instead are driven by geographic variation in genetic quality or parental effects.

Geographical variation in abiotic and biotic conditions can significantly affect the rate that an invasive species expands its range. The colonisation of Australia by cane toads (Rhinella marina) has attracted extensive research, but mostly in tropical regions rather than cooler climatic zones. We assembled multiple datasets to characterise the historical spread of toads at their southern (cool-climate) invasion front in north-eastern New South Wales (NSW). Perhaps because toads are relatively easy to find, visual and acoustic surveys appear to be as effective as eDNA-based surveys in detecting the species’ presence. Expansion of the toads’ range in NSW has occurred through the establishment of satellite populations as well as by growth of the range-core. Overall rates of spread have been more than tenfold lower than on the tropical front (means of <5 km vs. >50 km per year), and in some decades, the toads’ southern range has declined rather than expanded. Overall rates of spread since 1970 have accelerated to the south (through coastal habitats), but not to the west (into montane areas). The toads’ range has expanded most rapidly in decades with dry, warm weather conditions, but predicted future changes to climate are likely to have only minor effects on rates of toad spread. Understanding historical patterns of toad invasion in NSW can clarify probable future spread, and hence identify priority areas for control programs.

Methods

Data on the distribution of invasive cane toads in New South Wales was collated from all available sources, to quantify rates of expansion and to identify correlates of that rate of spread. We also conducted pilot studies to comapre alternative emthods of detecting invasion-front populations of toads in the field.

Usage Notes

The Excel sheet provides data for 342 points that represent the edges of the toad invasion front across a series of decades for which data are available. The dataset also includes climatic and habitat attributes of each of those sites, as determined from relevant GIS layers, as well as estimates of interdecadal changes in the location of the toads' range-edge.

Plos one raw data (native tad vs toad tad)Survival rate, svl, and weight of cane toad tadpole in Ishikgai island, Japan

Adult toads were collected at sites in tropical and temperate-zone eastern Australia. The toads were bred in captivity and their progeny raised at a series of controlled temperatures so that we could evaluate effects of larval temperatures on life-history traits.

Invasions often accelerate through time, as dispersal-enhancing traits accumulate at the expanding range edge. How does the dispersal behaviour of individual organisms shift to increase rates of population spread? We collate data from 44 radio-tracking studies (in total, of 650 animals) of cane toads (Rhinella marina) to quantify distances moved per day, and the frequency of displacement in their native range (French Guiana) and two invaded areas (Hawai’i and Australia). Here we show that toads in their native-range, Hawai’i and eastern Australia are relatively sedentary, while toads dispersing across tropical Australia increased their daily distances travelled from 20 to 200 m per day. That increase reflects an increasing propensity to change diurnal retreat sites every day, as well as to move further during each nocturnal displacement. Daily changes in retreat site evolved earlier than did changes in distances moved per night, indicating a breakdown in philopatry before other movement behaviours were optimised to maximise dispersal.

Methods Cane toads were radio-tracked using waistbelts holding small transmitters. Locations were recorded daily for 5 days, providing information on distances moved between successive diurnal retreat-sites, and the proportion of nights on which taods changed shelter-sites. For this paper, data were colelcted fro mmany such studies over a wide area, to explore changes in dispersal-related traits during the toad's invasion history.

Abstract We studied a population of large varanid lizards (yellow-spotted monitors Varanus panoptes) on a floodplain in tropical Australia. Growth records from radio-tracked lizards show that despite their large adult body sizes (to > 7 kg in males), these lizards attained sexual maturity at less than one year of age, and rarely lived for more than two years (females) or four years (males), even before mortality increased due to the arrival of toxic cane toads. This is a “faster†life-history than has been reported for other species of large monitors. Growth was especially rapid in males during the wet-season. The low survivorship prior to toad invasion was due to predation by pythons; communal nesting by female varanids may render them especially vulnerable. The life history of yellow-spotted monitors requires high feeding rates, favouring the evolution of “risky†tactics such as consuming novel prey items (such as cane toads); and the combination of high abundance (> 20 adult li..., Data collection: Radio telemetry Between November 2013 and January 2016 we radio†tracked 110 yellow†spotted monitors (Female lizards n= 52; Male lizards n= 58). During 15 three-week-long field trips, we searched for monitors between 0500 h and 1100 h each day; hence, new individuals were recruited to the study through time. By collaborating with indigenous rangers, we were able to collect lizards exhibiting a wide array of behavioural phenotypes (Ward-Fear et al. 2018, 2019). Monitors were captured by hand and transported back to the research station where we recorded snout†to†vent length (SVL) and body mass and took tissue samples from the tail tip for genetic sex determination (see Appendix for methodology). We attached a Very High Frequency (VHF) radio transmitter to the tail of each monitor (Holohil RI†2B, 15 g, < 5% total body mass) following the methods of Madsen and Ujvari (2009) and released the lizard back into the field at its point of capture within 6 h; telemetry began th..., , # Live fast, die young: life history traits of an apex predator exacerbate the ecological impact of a toxic invader.

https://doi.org/10.5061/dryad.jwstqjqks

Description of the data and file structure

This data was collected through an intensive radio telemetry project with the species in question, Varanus panoptes. The study was conducted in the Kimberley region of tropical Australia, specifically on a floodplain at Oombulgurri, to investigate the ecology and life history of the yellow-spotted monitor (Varanus panoptes) in a wet-dry climate. The research focused on understanding the impacts of cane toads on monitor populations, particularly mortality rates and age distribution. Data collection included radiotelemetry tracking of 110 monitors to assess growth rates, reproductive behaviors, and prey consumption, while also estimating population density and abundance through direct sightings and captures.

The study was divided into seve...